Calendaring extensions N. Jenkins Internet-Draft R. Stepanek Intended status: Standards Track Fastmail Expires: January 24, 2020 July 23, 2019 JSCalendar: A JSON representation of calendar data draft-ietf-calext-jscalendar-18 Abstract This specification defines a data model and JSON representation of calendar data that can be used for storage and data exchange in a calendaring and scheduling environment. It aims to be an alternative, and over time successor to, the widely deployed iCalendar data format and to be unambiguous, extendable and simple to process. In contrast to the JSON-based jCal format, it is not a direct mapping from iCalendar and expands semantics where appropriate. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 24, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Jenkins & Stepanek Expires January 24, 2020 [Page 1] Internet-Draft JSCalendar July 2019 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Motivation and Relation to iCalendar and jCal . . . . . . 5 1.2. Notational Conventions . . . . . . . . . . . . . . . . . 5 1.3. Type Signatures . . . . . . . . . . . . . . . . . . . . . 6 1.4. Data Types . . . . . . . . . . . . . . . . . . . . . . . 6 1.4.1. Int . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.4.2. UnsignedInt . . . . . . . . . . . . . . . . . . . . . 6 1.4.3. UTCDateTime . . . . . . . . . . . . . . . . . . . . . 7 1.4.4. LocalDateTime . . . . . . . . . . . . . . . . . . . . 7 1.4.5. Duration . . . . . . . . . . . . . . . . . . . . . . 7 1.4.6. SignedDuration . . . . . . . . . . . . . . . . . . . 8 1.4.7. Id . . . . . . . . . . . . . . . . . . . . . . . . . 8 1.4.8. PatchObject . . . . . . . . . . . . . . . . . . . . . 8 1.4.9. Time Zones . . . . . . . . . . . . . . . . . . . . . 9 2. JSCalendar Objects . . . . . . . . . . . . . . . . . . . . . 9 2.1. JSEvent . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2. JSTask . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3. JSGroup . . . . . . . . . . . . . . . . . . . . . . . . . 10 3. Structure of JSCalendar Objects . . . . . . . . . . . . . . . 10 3.1. Normalization and Equivalence . . . . . . . . . . . . . . 10 3.2. Custom Property Extensions and Values . . . . . . . . . . 11 4. Common JSCalendar Properties . . . . . . . . . . . . . . . . 11 4.1. Metadata Properties . . . . . . . . . . . . . . . . . . . 11 4.1.1. @type . . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.2. uid . . . . . . . . . . . . . . . . . . . . . . . . . 12 4.1.3. relatedTo . . . . . . . . . . . . . . . . . . . . . . 12 4.1.4. prodId . . . . . . . . . . . . . . . . . . . . . . . 13 4.1.5. created . . . . . . . . . . . . . . . . . . . . . . . 13 4.1.6. updated . . . . . . . . . . . . . . . . . . . . . . . 13 4.1.7. sequence . . . . . . . . . . . . . . . . . . . . . . 13 4.1.8. method . . . . . . . . . . . . . . . . . . . . . . . 14 4.2. What and Where Properties . . . . . . . . . . . . . . . . 14 4.2.1. title . . . . . . . . . . . . . . . . . . . . . . . . 14 4.2.2. description . . . . . . . . . . . . . . . . . . . . . 14 4.2.3. descriptionContentType . . . . . . . . . . . . . . . 14 4.2.4. showWithoutTime . . . . . . . . . . . . . . . . . . . 14 4.2.5. locations . . . . . . . . . . . . . . . . . . . . . . 15 4.2.6. virtualLocations . . . . . . . . . . . . . . . . . . 16 4.2.7. links . . . . . . . . . . . . . . . . . . . . . . . . 16 4.2.8. locale . . . . . . . . . . . . . . . . . . . . . . . 18 4.2.9. keywords . . . . . . . . . . . . . . . . . . . . . . 18 4.2.10. categories . . . . . . . . . . . . . . . . . . . . . 18 Jenkins & Stepanek Expires January 24, 2020 [Page 2] Internet-Draft JSCalendar July 2019 4.2.11. color . . . . . . . . . . . . . . . . . . . . . . . . 18 4.3. Recurrence Properties . . . . . . . . . . . . . . . . . . 19 4.3.1. recurrenceId . . . . . . . . . . . . . . . . . . . . 19 4.3.2. recurrenceRule . . . . . . . . . . . . . . . . . . . 19 4.3.3. recurrenceOverrides . . . . . . . . . . . . . . . . . 27 4.3.4. excluded . . . . . . . . . . . . . . . . . . . . . . 28 4.4. Sharing and Scheduling Properties . . . . . . . . . . . . 28 4.4.1. priority . . . . . . . . . . . . . . . . . . . . . . 28 4.4.2. freeBusyStatus . . . . . . . . . . . . . . . . . . . 29 4.4.3. privacy . . . . . . . . . . . . . . . . . . . . . . . 29 4.4.4. replyTo . . . . . . . . . . . . . . . . . . . . . . . 30 4.4.5. participants . . . . . . . . . . . . . . . . . . . . 31 4.5. Alerts Properties . . . . . . . . . . . . . . . . . . . . 35 4.5.1. useDefaultAlerts . . . . . . . . . . . . . . . . . . 35 4.5.2. alerts . . . . . . . . . . . . . . . . . . . . . . . 35 4.6. Multilingual Properties . . . . . . . . . . . . . . . . . 37 4.6.1. localizations . . . . . . . . . . . . . . . . . . . . 37 4.7. Time Zone Properties . . . . . . . . . . . . . . . . . . 37 4.7.1. timeZone . . . . . . . . . . . . . . . . . . . . . . 38 4.7.2. timeZones . . . . . . . . . . . . . . . . . . . . . . 38 5. Type-specific JSCalendar Properties . . . . . . . . . . . . . 40 5.1. JSEvent Properties . . . . . . . . . . . . . . . . . . . 40 5.1.1. start . . . . . . . . . . . . . . . . . . . . . . . . 40 5.1.2. duration . . . . . . . . . . . . . . . . . . . . . . 40 5.1.3. status . . . . . . . . . . . . . . . . . . . . . . . 41 5.2. JSTask Properties . . . . . . . . . . . . . . . . . . . . 41 5.2.1. due . . . . . . . . . . . . . . . . . . . . . . . . . 41 5.2.2. start . . . . . . . . . . . . . . . . . . . . . . . . 41 5.2.3. estimatedDuration . . . . . . . . . . . . . . . . . . 41 5.2.4. statusUpdatedAt . . . . . . . . . . . . . . . . . . . 41 5.2.5. progress . . . . . . . . . . . . . . . . . . . . . . 42 5.2.6. status . . . . . . . . . . . . . . . . . . . . . . . 42 5.3. JSGroup Properties . . . . . . . . . . . . . . . . . . . 43 5.3.1. entries . . . . . . . . . . . . . . . . . . . . . . . 44 5.3.2. source . . . . . . . . . . . . . . . . . . . . . . . 44 6. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 44 6.1. Simple Event . . . . . . . . . . . . . . . . . . . . . . 44 6.2. Simple Task . . . . . . . . . . . . . . . . . . . . . . . 44 6.3. Simple Group . . . . . . . . . . . . . . . . . . . . . . 45 6.4. All-day Event . . . . . . . . . . . . . . . . . . . . . . 45 6.5. Task with a Due Date . . . . . . . . . . . . . . . . . . 46 6.6. Event with End Time Zone . . . . . . . . . . . . . . . . 46 6.7. Floating-time Event (with Recurrence) . . . . . . . . . . 47 6.8. Event with Multiple Locations and Localization . . . . . 47 6.9. Recurring Event with Overrides . . . . . . . . . . . . . 48 6.10. Recurring Event with Participants . . . . . . . . . . . . 49 7. Security Considerations . . . . . . . . . . . . . . . . . . . 51 7.1. Expanding Recurrences . . . . . . . . . . . . . . . . . . 51 Jenkins & Stepanek Expires January 24, 2020 [Page 3] Internet-Draft JSCalendar July 2019 7.2. JSON Parsing . . . . . . . . . . . . . . . . . . . . . . 51 7.3. URI Values . . . . . . . . . . . . . . . . . . . . . . . 52 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 52 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 53 10.1. Normative References . . . . . . . . . . . . . . . . . . 53 10.2. Informative References . . . . . . . . . . . . . . . . . 55 10.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56 1. Introduction This document defines a data model for calendar event and task objects, or groups of such objects, in electronic calendar applications and systems. It aims to be unambiguous, extendable and simple to process. The key design considerations for this data model are as follows: o The attributes of the calendar entry represented must be described as a simple key-value pair. Simple events are simple to represent, complex events can be modelled accurately. o Wherever possible, there should be only one way to express the desired semantics, reducing complexity. o The data model should avoid ambiguities and make it difficult to make mistakes during implementation. o The data model should be compatible with the iCalendar data format [RFC5545] [RFC7986] and extensions, but the specification should add new attributes where the iCalendar format currently lacks expressivity, and drop widely unused, obsolete or redundant properties. This means translation with no loss of semantics should be easy with most common iCalendar files but is not guaranteed with the full specification. o Extensions, such as new properties and components, MUST NOT lead to requiring an update to this document. The representation of this data model is defined in the I-JSON format [RFC7493], which is a strict subset of the JavaScript Object Notation (JSON) Data Interchange Format [RFC8259]. Using JSON is mostly a pragmatic choice: its widespread use makes JSCalendar easier to adopt, and the ready availability of production-ready JSON implementations eliminates a whole category of parser-related interoperability issues, which iCalendar has often suffered from. Jenkins & Stepanek Expires January 24, 2020 [Page 4] Internet-Draft JSCalendar July 2019 1.1. Motivation and Relation to iCalendar and jCal The iCalendar data format [RFC5545], a widely deployed interchange format for calendaring and scheduling data, has served calendaring vendors for a long while, but contains some ambiguities and pitfalls that can not be overcome without backward-incompatible changes. For example, iCalendar defines various formats for local times, UTC time and dates, which confuses new users and often leads to implementation errors. Other sources for errors are the requirement for custom time zone definitions within a single calendar component, as well as the iCalendar format itself; the latter causing interoperability issues due to misuse of CR LF terminated strings, line continuations and subtle differences between iCalendar parsers. The definition of recurrence rules is ambiguous and has resulted in differing understandings even between experienced calendar developers. In recent years, many new products and services have appeared that wish to use a JSON representation of calendar data within their API. The JSON format for iCalendar data, jCal [RFC7265], is a direct mapping between iCalendar and JSON. In its effort to represent full iCalendar semantics, it inherits all the same pitfalls and uses a complicated JSON structure unlike most common JSON data representations. As a consequence, since the standardization of jCal, the majority of implementations and service providers either kept using iCalendar, or came up with their own proprietary JSON representations, which are incompatible with each other and often suffer from common pitfalls, such as storing event start times in UTC (which become incorrect if the timezone's rules change in the future). JSCalendar is intended to meet this demand for JSON-formatted calendar data, and to provide a standard, elegant representation as an alternative to new proprietary formats. 1.2. Notational Conventions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. The underlying format used for this specification is JSON. Consequently, the terms "object" and "array" as well as the four primitive types (strings, numbers, booleans, and null) are to be interpreted as described in Section 1 of [RFC8259]. Jenkins & Stepanek Expires January 24, 2020 [Page 5] Internet-Draft JSCalendar July 2019 Some examples in this document contain "partial" JSON documents used for illustrative purposes. In these examples, three periods "..." are used to indicate a portion of the document that has been removed for compactness. 1.3. Type Signatures Type signatures are given for all JSON values in this document. The following conventions are used: o "*" - The type is undefined (the value could be any type, although permitted values may be constrained by the context of this value). o "String" - The JSON string type. o "Number" - The JSON number type. o "Boolean" - The JSON boolean type. o "A[B]" - A JSON object where the keys are all of type "A", and the values are all of type "B". o "A[]" - An array of values of type "A". o "A|B" - The value is either of type "A" or of type "B". Other types may also be given, with their representation defined elsewhere in this document. 1.4. Data Types In addition to the standard JSON data types, the following data types are used in this specification: 1.4.1. Int Where "Int" is given as a data type, it means an integer in the range -2^53+1 <= value <= 2^53-1, the safe range for integers stored in a floating-point double, represented as a JSON "Number". 1.4.2. UnsignedInt Where "UnsignedInt" is given as a data type, it means an "Int" where the value MUST be in the range 0 <= value <= 2^53-1. Jenkins & Stepanek Expires January 24, 2020 [Page 6] Internet-Draft JSCalendar July 2019 1.4.3. UTCDateTime This is a string in [RFC3339] "date-time" format, with the further restrictions that any letters MUST be in uppercase, the time component MUST be included and the time offset MUST be the character "Z". Fractional second values MUST NOT be included unless non-zero and MUST NOT have trailing zeros, to ensure there is only a single representation for each date-time. For example "2010-10-10T10:10:10.003Z" is OK, but "2010-10-10T10:10:10.000Z" is invalid and MUST be encoded as "2010-10-10T10:10:10Z". In common notation, it should be of the form "YYYY-MM-DDTHH:MM:SSZ". 1.4.4. LocalDateTime This is a date-time string with no time zone/offset information. It is otherwise in the same format as UTCDateTime, including fractional seconds. For example "2006-01-02T15:04:05" and "2006-01-02T15:04:05.003" are both valid. The time zone to associate the LocalDateTime with comes from an associated property, or if no time zone is associated it defines *floating time*. Floating date- times are not tied to any specific time zone. Instead, they occur in every time zone at the same wall-clock time (as opposed to the same instant point in time). 1.4.5. Duration Where Duration is given as a type, it means a length of time represented by a subset of ISO8601 duration format, as specified by the following ABNF: dur-secfrac = "." 1*DIGIT dur-second = 1*DIGIT [dur-secfrac] "S" dur-minute = 1*DIGIT "M" [dur-second] dur-hour = 1*DIGIT "H" [dur-minute] dur-time = "T" (dur-hour / dur-minute / dur-second) dur-day = 1*DIGIT "D" dur-week = 1*DIGIT "W" duration = "P" (dur-day [dur-time] / dur-time / dur-week) In addition, the duration MUST NOT include fractional second values unless the fraction is non-zero. Jenkins & Stepanek Expires January 24, 2020 [Page 7] Internet-Draft JSCalendar July 2019 1.4.6. SignedDuration A SignedDuration represents a length of time that may be positive or negative and is typically used to express the offset of a point in time relative to an associated time. It is represented as a Duration, optionally preceded by a sign character. It is specified by the following ABNF: signed-duration = (["+"] / "-") duration A negative sign indicates a point in time at or before the associated time, a positive or no sign a time at or after the associated time. 1.4.7. Id Where "Id" is given as a data type, it means a "String" of at least 1 and a maximum of 255 octets in size, and it MUST only contain characters from the "URL and Filename Safe" base64 alphabet, as defined in Section 5 of [RFC4648], excluding the pad character ("="). This means the allowed characters are the ASCII alphanumeric characters ("A-Za-z0-9"), hyphen ("-"), and underscore ("_"). Unless otherwise specified, Ids are arbitrary and only have meaning within the object where they are being used. Ids need not be unique between different objects. For example, two JSEvent objects MAY use the same ids in their respective "links" properties. Or within the same JSEvent object the same Id could appear in the "participants" and "alerts" properties. This does not imply any semantic connection between the two. Nevertheless, a UUID is typically a good choice. 1.4.8. PatchObject A PatchObject is of type "String[*]", and represents an unordered set of patches on a JSON object. The keys are a path in a subset of [RFC6901] JSON pointer format, with an implicit leading "/" (i.e. prefix each key with "/" before applying the JSON pointer evaluation algorithm). A patch within a PatchObject is only valid if all of the following conditions apply: 1. The pointer MUST NOT reference inside an array (i.e. it MUST NOT insert/delete from an array; the array MUST be replaced in its entirety instead). Jenkins & Stepanek Expires January 24, 2020 [Page 8] Internet-Draft JSCalendar July 2019 2. When evaluating a path, all parts prior to the last (i.e. the value after the final slash) MUST exist. 3. There MUST NOT be two patches in the PatchObject where the pointer of one is the prefix of the pointer of the other, e.g. "alerts/foo/offset" and "alerts". The value associated with each pointer is either: o null: Remove the property from the patched object. If not present in the parent, this a no-op. o Anything else: The value to set for this property (this may be a replacement or addition to the object being patched). Implementations MUST reject a PatchObject if any of its patches are invalid. 1.4.9. Time Zones By default, time zones in JSCalendar are identified by their name in the IANA Time Zone Database [1], and the zone rules of the respective zone record apply. Implementations MAY embed the definition of custom time zones in the "timeZones" property (see Section 4.7.2). 2. JSCalendar Objects This section describes the calendar object types specified by JSCalendar. 2.1. JSEvent MIME type: "application/jscalendar+json;type=jsevent" A JSEvent represents a scheduled amount of time on a calendar, typically a meeting, appointment, reminder or anniversary. Multiple participants may partake in the event at multiple locations. The @type (Section 4.1.1) property value MUST be "jsevent". 2.2. JSTask MIME type: "application/jscalendar+json;type=jstask" A JSTask represents an action-item, assignment, to-do or work item. Jenkins & Stepanek Expires January 24, 2020 [Page 9] Internet-Draft JSCalendar July 2019 The @type (Section 4.1.1) property value MUST be "jstask". A JSTask may start and be due at certain points in time, may take some estimated time to complete and may recur; none of which is required. This notably differs from JSEvent (Section 2.1) which is required to start at a certain point in time and typically takes some non-zero duration to complete. 2.3. JSGroup MIME type: "application/jscalendar+json;type=jsgroup" A JSGroup is a collection of JSEvent (Section 2.1) and/or JSTask (Section 2.2) objects. Typically, objects are grouped by topic (e.g. by keywords) or calendar membership. The @type (Section 4.1.1) property value MUST be "jsgroup". 3. Structure of JSCalendar Objects A JSCalendar object is a JSON object, which MUST be valid I-JSON (a stricter subset of JSON), as specified in [RFC8259]. Property names and values are case-sensitive. The object has a collection of properties, as specified in the following sections. Properties are specified as being either mandatory or optional. Optional properties may have a default value, if explicitly specified in the property definition. 3.1. Normalization and Equivalence JSCalendar aims to provide unambiguous definitions for value types and properties, but does not define a general normalization or equivalence method for JSCalendar objects and types. This is because the notion of equivalence might range from byte-level equivalence to semantic equivalence, depending on the respective use case (for example, the CalDAV protocol [RFC4791] requires octet equivalence of the encoded calendar object to determine ETag equivalence). Normalization of JSCalendar objects is hindered because of the following reasons: o Custom JSCalendar properties may contain arbitrary JSON values, including arrays. However, equivalence of arrays might or might not depend on the order of elements, depending on the respective property definition. Jenkins & Stepanek Expires January 24, 2020 [Page 10] Internet-Draft JSCalendar July 2019 o Several JSCalendar property values are defined as URIs and MIME types, but normalization of these types is inherently protocol and scheme-specific, depending on the use-case of the equivalence definition (see Section 6 of [RFC3986]). Considering this, the definition of equivalence and normalization is left to client and server implementations and to be negotiated by a calendar exchange protocol or defined by another RFC. 3.2. Custom Property Extensions and Values Vendors MAY add additional properties to the calendar object to support their custom features. The names of these properties MUST be prefixed with a domain name controlled by the vendor to avoid conflict, e.g. "example.com/customprop". Some JSCalendar properties allow vendor-specific value extensions. If so, vendor specific values MUST be prefixed with a domain name controlled by the vendor, e.g. "example.com/customrel", unless otherwise noted. Vendors are strongly encouraged to standardize any new property values or extensions that are useful to other systems as well, rather than use a vendor-specific prefix. 4. Common JSCalendar Properties This section describes the properties that are common to the various JSCalendar object types. Specific JSCalendar object types may only support a subset of these properties. The object type definitions in Section 5 describe the set of supported properties per type. 4.1. Metadata Properties 4.1.1. @type Type: "String" (mandatory). Specifies the type which this object represents. This MUST be one of the following values, registered in a future RFC, or a vendor- specific value: o "jsevent": a JSCalendar event (Section 2.1). o "jstask": a JSCalendar task (Section 2.2). o "jsgroup": a JSCalendar group (Section 2.3). Jenkins & Stepanek Expires January 24, 2020 [Page 11] Internet-Draft JSCalendar July 2019 4.1.2. uid Type: "String" (mandatory). A globally unique identifier, used to associate the object as the same across different systems, calendars and views. The value of this property MUST be unique across all JSCalendar objects, even if they are of different type. [RFC4122] describes a range of established algorithms to generate universally unique identifiers (UUID), and the random or pseudo-random version is recommended. For compatibility with [RFC5545] UIDs, implementations MUST be able to receive and persist values of at least 255 octets for this property, but they MUST NOT truncate values in the middle of a UTF-8 multi-octet sequence. 4.1.3. relatedTo Type: "String[Relation]" (optional). Relates the object to other JSCalendar objects. This is represented as a map of the UIDs of the related objects to information about the relation. A Relation object has the following property: o relation: "String[Boolean]" (optional) Describes how the linked object is related to this object as a set of relation types. If specified, the set MUST NOT be empty. If ommitted, the relationship between the two objects is unspecified. Keys in the set MUST be one of the following values, defined in a future specification or a vendor-specific value: * "first": The linked object is the first in the series this object is part of. * "next": The linked object is the next in the series this object is part of. * "child": The linked object is a subpart of this object. * "parent": This object is part of the overall linked object. The value for each key in the set MUST be true. Jenkins & Stepanek Expires January 24, 2020 [Page 12] Internet-Draft JSCalendar July 2019 Note, the Relation object only has one property; it is specified as an object with a single property rather than mapping directly from the UID to relation types to allow for extension in the future. If an object is split to make a "this and future" change to a recurrence, the original object MUST be truncated to end at the previous occurrence before this split, and a new object created to represent all the occurrences after the split. A "next" relation MUST be set on the original object's relatedTo property for the UID of the new object. A "first" relation for the UID of the first object in the series MUST be set on the new object. Clients can then follow these UIDs to get the complete set of objects if the user wishes to modify them all at once. 4.1.4. prodId Type: "String" (optional). The identifier for the product that created the JSCalendar object. The vendor of the implementation SHOULD ensure that this is a globally unique identifier, using some technique such as an FPI value, as defined in [ISO.9070.1991]. It MUST only use characters of an iCalendar TEXT data value (see Section 3.3.11 of [RFC5545]). This property SHOULD NOT be used to alter the interpretation of a JSCalendar object beyond the semantics specified in this document. For example, it is not to be used to further the understanding of non-standard properties. 4.1.5. created Type: "UTCDateTime" (optional). The date and time this object was initially created. 4.1.6. updated Type: "UTCDateTime" (mandatory). The date and time the data in this object was last modified. 4.1.7. sequence Type: "UnsignedInt" (optional, default: 0). Jenkins & Stepanek Expires January 24, 2020 [Page 13] Internet-Draft JSCalendar July 2019 Initially zero, this MUST be incremented by one every time a change is made to the object, except if the change only modifies the "participants" property (see Section 4.4.5). This is used as part of iTIP [RFC5546] to know which version of the object a scheduling message relates to. 4.1.8. method Type: "String" (optional). The iTIP [RFC5546] method, in lowercase. This MUST only be present if the JSCalendar object represents an iTIP scheduling message. 4.2. What and Where Properties 4.2.1. title Type: "String" (optional, default: empty String). A short summary of the object. 4.2.2. description Type: "String" (optional, default: empty String). A longer-form text description of the object. The content is formatted according to the "descriptionContentType" property. 4.2.3. descriptionContentType Type: "String" (optional, default: "text/plain"). Describes the media type [RFC6838] of the contents of the "description" property. Media types MUST be sub-types of type "text", and SHOULD be "text/plain" or "text/html" [MIME]. They MAY define parameters and the "charset" parameter value MUST be "utf-8", if specified. Descriptions of type "text/html" MAY contain "cid" URLs [RFC2392] to reference links in the calendar object by use of the "cid" property of the Link object. 4.2.4. showWithoutTime Type: "Boolean" (optional, default: false). Indicates the time is not important to display to the user when rendering this calendar object, for example an event that conceptually occurs all day or across multiple days, such as "New Jenkins & Stepanek Expires January 24, 2020 [Page 14] Internet-Draft JSCalendar July 2019 Year's Day" or "Italy Vacation". While the time component is important for free-busy calculations and checking for scheduling clashes, calendars may choose to omit displaying it and/or display the object separately to other objects to enhance the user's view of their schedule. Such events are also commonly known as "all-day" events. 4.2.5. locations Type: "Id[Location]" (optional). A map of location ids to Location objects, representing locations associated with the object. A Location object has the following properties. It MUST have at least one property other than the "relativeTo" property. o name: "String" (optional) The human-readable name of the location. o description: "String" (optional) Human-readable, plain-text instructions for accessing this location. This may be an address, set of directions, door access code, etc. o relativeTo: "String" (optional) The relation type of this location to the JSCalendar object. This MUST be either one of the following values, registered in a future RFC, or a vendor-specific value. Any value the client or server doesn't understand should be treated the same as if this property is omitted. * "start": The JSCalendar object starts at this location. * "end": The JSCalendar object ends at this location. o timeZone: "String" (optional) A time zone for this location. See also Section 1.4.9. o coordinates: "String" (optional) A "geo:" URI [RFC5870] for the location. Jenkins & Stepanek Expires January 24, 2020 [Page 15] Internet-Draft JSCalendar July 2019 o linkIds: "Id[Boolean]" (optional) A set of link ids for links to alternate representations of this location. Each key in the set MUST be the id of a Link object defined in the "links" property of this calendar object. The value for each key in the set MUST be true. This MUST be omitted if none (rather than an empty set). For example, an alternative representation could be in vCard format. 4.2.6. virtualLocations Type: "Id[VirtualLocation]" (optional). A map of ids to VirtualLocation objects, representing virtual locations, such as video conferences or chat rooms, associated with the object. A VirtualLocation object has the following properties. o name: "String" (optional, default: empty String) The human-readable name of the virtual location. o description: "String" (optional) Human-readable plain-text instructions for accessing this location. This may be an address, set of directions, door access code, etc. o uri: "String" (mandatory) A URI that represents how to connect to this virtual location. This may be a telephone number (represented using the "tel:" scheme, e.g., "tel:+1-555-555-555") for a teleconference, a web address for online chat, or any custom URI. 4.2.7. links Type: "Id[Link]" (optional). A map of link ids to Link objects, representing external resources associated with the object. A Link object has the following properties: Jenkins & Stepanek Expires January 24, 2020 [Page 16] Internet-Draft JSCalendar July 2019 o href: "String" (mandatory) A URI from which the resource may be fetched. This MAY be a "data:" URL, but it is recommended that the file be hosted on a server to avoid embedding arbitrarily large data in JSCalendar object instances. o cid: "String" (optional) This MUST be a valid "content-id" value according to the definition of Section 2 in [RFC2392]. The value MUST be unique within this Link object but has no meaning beyond that. It MAY be different from the link id for this Link object. o type: "String" (optional) The content-type [RFC6838] of the resource, if known. o size: "UnsignedInt" (optional) The size, in octets, of the resource when fully decoded (i.e. the number of octets in the file the user would download), if known. o rel: "String" (optional) Identifies the relation of the linked resource to the object. If set, the value MUST be a registered relation type (see [RFC8288] and IANA Link Relations [2]). Links with a rel of "enclosure" SHOULD be considered by the client as attachments for download. Links with a rel of "describedby" SHOULD be considered by the client to be an alternate representation of the description. Links with a rel of "icon" SHOULD be considered by the client to be an image that it MAY use when presenting the calendar data to a user. The "display" property MAY be set to indicate the purpose of this image. o display: "String" (optional) Describes the intended purpose of a link to an image. If set, the "rel" property MUST be set to "icon". The value MUST be either one of the following values, registered in a future RFC, or a vendor-specific value: Jenkins & Stepanek Expires January 24, 2020 [Page 17] Internet-Draft JSCalendar July 2019 * "badge": an image inline with the title of the object. * "graphic": a full image replacement for the object itself. * "fullsize": an image that is used to enhance the object. * "thumbnail": a smaller variant of "fullsize" to be used when space for the image is constrained. o title: "String" (optional) A human-readable plain-text description of the resource. 4.2.8. locale Type: "String" (optional). The language tag as defined in [RFC5646] that best describes the locale used for the text in the calendar object, if known. 4.2.9. keywords Type: "String[Boolean]" (optional). A set of keywords or tags that relate to the object. The set is represented as a map, with the keys being the keywords. The value for each key in the map MUST be true. 4.2.10. categories Type: "String[Boolean]" (optional). A set of categories that relate to the calendar object. The set is represented as a map, with the keys being the categories specified as URIs. The value for each key in the map MUST be true. In contrast to keywords, categories typically are structured. For example, a vendor owning the domain "example.com" might define the categories "http://example.com/categories/sports/american-football"" and "http://example.com/categories/music/r-b". 4.2.11. color Type: "String" (optional). A color clients MAY use when displaying this calendar object. The value is a case-insensitive color name taken from the CSS3 set of Jenkins & Stepanek Expires January 24, 2020 [Page 18] Internet-Draft JSCalendar July 2019 names, defined in Section 4.3 of W3C.REC-css3-color-20110607 [3] or a CSS3 RGB color hex value. 4.3. Recurrence Properties Some events and tasks occur at regular, or indeed irregular, intervals. Rather than having to copy the data for every occurrence, you can instead have a master event with a recurrence rule generating the occurrences, and/or overrides that add extra dates or exceptions to the rule. 4.3.1. recurrenceId Type: "LocalDateTime" (optional). If present, this JSCalendar object represents one occurrence of a recurring JSCalendar object. If present the "recurrenceRule" and "recurrenceOverrides" properties MUST NOT be present. The value is a date-time either produced by the "recurrenceRule" of the master event, or added as a key to the "recurrenceOverrides" property of the master event. 4.3.2. recurrenceRule Type: "Recurrence" (optional). Defines a recurrence rule (repeating pattern) for recurring calendar objects. A JSEvent recurs by applying the recurrence rule to the "start" date- time. A JSTask recurs by applying the recurrence rule to the "start" date- time, if defined, otherwise it recurs by the "due" date-time, if defined. If the task defines neither a "start" nor "due" date-time, its "recurrenceRule" property value MUST be null. A Recurrence object is a JSON object mapping of a RECUR value type in iCalendar [RFC5545] [RFC7529] and has the same semantics. It has the following properties: o frequency: "String" (mandatory) The time span covered by each iteration of this recurrence rule (see Section 4.3.2.1 for full semantics). This MUST be one of the following values: Jenkins & Stepanek Expires January 24, 2020 [Page 19] Internet-Draft JSCalendar July 2019 * "yearly" * "monthly" * "weekly" * "daily" * "hourly" * "minutely" * "secondly" This is the FREQ part from iCalendar, converted to lowercase. o interval: "UnsignedInt" (optional, default: 1) The interval of iteration periods at which the recurrence repeats. If included, it MUST be an integer >= 1. This is the INTERVAL part from iCalendar. o rscale: "String" (optional, default: "gregorian") The calendar system in which this recurrence rule operates, in lowercase. This MUST be either a CLDR-registered calendar system name, or a non-standard, experimental calendar system name prefixed with the characters "x-". This is the RSCALE part from iCalendar RSCALE [RFC7529], converted to lowercase. o skip: "String" (optional, default: "omit") The behaviour to use when the expansion of the recurrence produces invalid dates. This MUST be one of the following values: * "omit" * "backward" * "forward" This is the SKIP part from iCalendar RSCALE [RFC7529], converted to lowercase. o firstDayOfWeek: "String" (optional, default: "mo") Jenkins & Stepanek Expires January 24, 2020 [Page 20] Internet-Draft JSCalendar July 2019 The day on which the week is considered to start, represented as a lowercase abbreviated two-letter English day of the week. If included, it MUST be one of the following values: * "mo" * "tu" * "we" * "th" * "fr" * "sa" * "su" This is the WKST part from iCalendar. o byDay: "NDay[]" (optional) Days of the week on which to repeat. An *NDay* object has the following properties: * day: "String" (mandatory) A day of the week on which to repeat; the allowed values are the same as for the "firstDayOfWeek" Recurrence property. This is the day-of-the-week of the BYDAY part in iCalendar, converted to lowercase. * nthOfPeriod: "Int" (optional) If present, rather than representing every occurrence of the weekday defined in the "day" property, it represents only a specific instance within the recurrence period. The value can be positive or negative, but MUST NOT be zero. A negative integer means nth-last of period. This is the ordinal part of the BYDAY value in iCalendar (e.g. 1 or -3). o byMonthDay: "Int[]" (optional) Jenkins & Stepanek Expires January 24, 2020 [Page 21] Internet-Draft JSCalendar July 2019 Days of the month on which to repeat. Valid values are 1 to 31 or -31 to -1. Negative values offset from the end of the month. The array MUST have at least one entry if included. This is the BYMONTHDAY part in iCalendar. o byMonth: "String[]" (optional) The months in which to repeat. Each entry is a string representation of a number, starting from "1" for the first month in the calendar (e.g. "1" means January with the Gregorian calendar), with an optional "L" suffix (see [RFC7529]) for leap months (this MUST be uppercase, e.g. "3L"). The array MUST have at least one entry if included. This is the BYMONTH part from iCalendar. o byYearDay: "Int[]" (optional) The days of the year on which to repeat. Valid values are 1 to 366 or -366 to -1. Negative values offset from the end of the year. The array MUST have at least one entry if included. This is the BYYEARDAY part from iCalendar. o byWeekNo: "Int[]" (optional) Weeks of the year in which to repeat. Valid values are 1 to 53 or -53 to -1. The array MUST have at least one entry if included. This is the BYWEEKNO part from iCalendar. o byHour: "UnsignedInt[]" (optional) The hours of the day in which to repeat. Valid values are 0 to 23. The array MUST have at least one entry if included. This is the BYHOUR part from iCalendar. o byMinute: "UnsignedInt[]" (optional) The minutes of the hour in which to repeat. Valid values are 0 to 59. The array MUST have at least one entry if included. This is the BYMINUTE part from iCalendar. o bySecond: "UnsignedInt[]" (optional) Jenkins & Stepanek Expires January 24, 2020 [Page 22] Internet-Draft JSCalendar July 2019 The seconds of the minute in which to repeat. Valid values are 0 to 60. The array MUST have at least one entry if included. This is the BYSECOND part from iCalendar. o bySetPosition: "Int[]" (optional) The occurrences within the recurrence interval to include in the final results. Negative values offset from the end of the list of occurrences. The array MUST have at least one entry if included. This is the BYSETPOS part from iCalendar. o count: "UnsignedInt" (optional) The number of occurrences at which to range-bound the recurrence. This MUST NOT be included if an "until" property is specified. This is the COUNT part from iCalendar. o until: "LocalDateTime" (optional) The date-time at which to finish recurring. The last occurrence is on or before this date-time. This MUST NOT be included if a "count" property is specified. Note: if not specified otherwise for a specific JSCalendar object, this date is to be interpreted in the time zone specified in the JSCalendar object's "timeZone" property. This is the UNTIL part from iCalendar. 4.3.2.1. Interpreting recurrence rules A recurrence rule specifies a set of date-times for recurring calendar objects. A recurrence rule has the following semantics. Note, wherever "year", "month" or "day of month" is used, this is within the calendar system given by the "rscale" property, which defaults to gregorian if omitted. 1. A set of candidates is generated. This is every second within a period defined by the frequency property value: * "yearly": every second from midnight on the 1st day of a year (inclusive) to midnight the 1st day of the following year (exclusive). If skip is not "omit", the calendar system has leap months and there is a byMonth property, generate candidates for the leap months even if they don't occur in this year. Jenkins & Stepanek Expires January 24, 2020 [Page 23] Internet-Draft JSCalendar July 2019 If skip is not "omit" and there is a byMonthDay property, presume each month has the maximum number of days any month may have in this calendar system when generating candidates, even if it's more than this month actually has. * "monthly": every second from midnight on the 1st day of a month (inclusive) to midnight on the 1st of the following month (exclusive). If skip is not "omit" and there is a byMonthDay property, presume the month has the maximum number of days any month may have in this calendar system when generating candidates, even if it's more than this month actually has. * "weekly": every second from midnight (inclusive) on the first day of the week (as defined by the firstDayOfWeek property, or Monday if omitted), to midnight 7 days later (exclusive). * "daily": every second from midnight at the start of the day (inclusive) to midnight at the end of the day (exclusive). * "hourly": every second from the beginning of the hour (inclusive) to the beginning of the next hour (exclusive). * "minutely": every second from the beginning of the minute (inclusive) to the beginning of the next minute (exclusive). * "secondly": the second itself, only. 2. Each date-time candidate is compared against all of the byX properties of the rule except bySetPosition. If any property in the rule does not match the date-time, it is eliminated. Each byX property is an array; the date-time matches the property if it matches any of the values in the array. The properties have the following semantics: * byMonth: the date-time is in the given month. * byWeekNo: the date-time is in the nth week of the year. Negative numbers mean the nth last week of the year. This corresponds to weeks according to week numbering as defined in ISO.8601.2004, with a week defined as a seven day period, starting on the firstDayOfWeek property value or Monday if omitted. Week number one of the calendar year is the first week that contains at least four days in that calendar year. Jenkins & Stepanek Expires January 24, 2020 [Page 24] Internet-Draft JSCalendar July 2019 If the date-time is not valid (this may happen when generating candidates with a skip property in effect), it is always eliminated by this property. * byYearDay: the date-time is on the nth day of year. Negative numbers mean the nth last day of the year. If the date-time is not valid (this may happen when generating candidates with a skip property in effect), it is always eliminated by this property. * byMonthDay: the date-time is on the given day of the month. Negative numbers mean the nth last day of the month. * byDay: the date-time is on the given day of the week. If the day is prefixed by a number, it is the nth occurrence of that day of the week within the month (if frequency is monthly) or year (if frequency is yearly). Negative numbers means nth last occurrence within that period. * byHour: the date-time has the given hour value. * byMinute: the date-time has the given minute value. * bySecond: the date-time has the given second value. If a skip property is defined and is not "omit", there may be candidates that do not correspond to valid dates (e.g. 31st February in the gregorian calendar). In this case, the properties MUST be considered in the order above and: 1. After applying the byMonth filter, if the candidate's month is invalid for the given year increment it (if skip is "forward") or decrement it (if skip is "backward") until a valid month is found, incrementing/decrementing the year as well if you pass through the beginning/end of the year. This only applies to calendar systems with leap months. 2. After applying the byMonthDay filter, if the day of the month is invalid for the given month and year, change the date to the first day of the next month (if skip == "forward") or the last day of the current month (if skip == "backward"). 3. If any valid date produced after applying the skip is already a candidate, eliminate the duplicate. (For example after adjusting, 30th February and 31st February would both become the same "real" date, so one is eliminated as a duplicate.) Jenkins & Stepanek Expires January 24, 2020 [Page 25] Internet-Draft JSCalendar July 2019 3. If a bySetPosition property is included, this is now applied to the ordered list of remaining dates. This property specifies the indexes of date-times to keep; all others should be eliminated. Negative numbers are indexes from the end of the list, with -1 being the last item. 4. Any date-times before the start date of the event are eliminated (see below for why this might be needed). 5. If a skip property is included and is not "omit", eliminate any date-times that have already been produced by previous iterations of the algorithm. (This is not possible if skip == "omit".) 6. If further dates are required (we have not reached the until date, or count limit) skip the next (interval - 1) sets of candidates, then continue from step 1. When determining the set of occurrence dates for an event or task, the following extra rules must be applied: 1. The initial date-time to which the rule is applied (the "start" date-time for events; the "start" or "due" date-time for tasks) is always the first occurrence in the expansion (and is counted if the recurrence is limited by a "count" property), even if it would normally not match the rule. 2. The first set of candidates to consider is that which would contain the initial date-time. This means the first set may include candidates before the initial date-time; such candidates are eliminated from the results in step (4) as outlined before. 3. The following properties MUST be implicitly added to the rule under the given conditions: * If frequency is not "secondly" and no bySecond property: Add a bySecond property with the sole value being the seconds value of the initial date-time. * If frequency is not "secondly" or "minutely", and no byMinute property: Add a byMinute property with the sole value being the minutes value of the initial date-time. * If frequency is not "secondly", "minutely" or "hourly" and no byHour property: Add a byHour property with the sole value being the hours value of the initial date-time. Jenkins & Stepanek Expires January 24, 2020 [Page 26] Internet-Draft JSCalendar July 2019 * If frequency is "weekly" and no byDay property: Add a byDay property with the sole value being the day-of-the-week of the initial date-time. * If frequency is "monthly" and no byDay property and no byMonthDay property: Add a byMonthDay property with the sole value being the day-of-the-month of the initial date-time. * If frequency is "yearly" and no byYearDay property: + If there are no byMonth or byWeekNo properties, and either there is a byMonthDay property or there is no byDay property: Add a byMonth property with the sole value being the month of the initial date-time. + If there is no byMonthDay, byWeekNo or byDay properties: Add a byMonthDay property with the sole value being the day-of-the-month of the initial date-time. + If there is a byWeekNo property and no byMonthDay or byDay properties: Add a byDay property with the sole value being the day-of-the-week of the initial date-time. 4.3.3. recurrenceOverrides Type: "LocalDateTime[PatchObject]" (optional). A map of the recurrence ids (the date-time produced by the recurrence rule) to an object of patches to apply to the generated occurrence object. If the recurrence id does not match a date-time from the recurrence rule (or no rule is specified), it is to be treated as an additional occurrence (like an RDATE from iCalendar). The patch object may often be empty in this case. If the patch object defines the "excluded" property value to be true, then the recurring calendar object does not occur at the recurrence id date-time (like an EXDATE from iCalendar). Such a patch object MUST NOT patch any other property. By default, an occurrence inherits all properties from the main object except the start (or due) date-time, which is shifted to match the recurrence id LocalDateTime. However, individual properties of the occurrence can be modified by a patch, or multiple patches. It is valid to patch the "start" property value, and this patch takes precedence over the value generated from the recurrence id. Both the Jenkins & Stepanek Expires January 24, 2020 [Page 27] Internet-Draft JSCalendar July 2019 recurrence id as well as the patched "start" date-time may occur before the original JSCalendar object's "start" or "due" date. A pointer in the PatchObject MUST be ignored if it starts with one of the following prefixes: o @type o method o prodId o recurrenceId o recurrenceOverrides o recurrenceRule o relatedTo o replyTo o uid 4.3.4. excluded Type: "Boolean" (optional, default: false). Defines if this object is an overridden, excluded instance of a recurring JSCalendar object (see Section 4.3.3). If this property value is true, this calendar object instance MUST be removed from the occurrence expansion. The absence of this property or its default value false indicates that this instance MUST be included in the occurrence expansion. 4.4. Sharing and Scheduling Properties 4.4.1. priority Type: "Int" (optional, default: 0). Specifies a priority for the calendar object. This may be used as part of scheduling systems to help resolve conflicts for a time period. The priority is specified as an integer in the range 0 to 9. A value of 0 specifies an undefined priority. A value of 1 is the highest priority. A value of 2 is the second highest priority. Subsequent Jenkins & Stepanek Expires January 24, 2020 [Page 28] Internet-Draft JSCalendar July 2019 numbers specify a decreasing ordinal priority. A value of 9 is the lowest priority. Other integer values are reserved for future use. 4.4.2. freeBusyStatus Type: "String" (optional, default: "busy"). Specifies how this property should be treated when calculating free- busy state. The value MUST be one of: o "free": The object should be ignored when calculating whether the user is busy. o "busy": The object should be included when calculating whether the user is busy. 4.4.3. privacy Type: "String" (optional, default: "public"). Calendar objects are normally collected together and may be shared with other users. The privacy property allows the object owner to indicate that it should not be shared, or should only have the time information shared but the details withheld. Enforcement of the restrictions indicated by this property are up to the API via which this object is accessed. This property MUST NOT affect the information sent to scheduled participants; it is only interpreted when the object is shared as part of a shared calendar. The value MUST be either one of the following values, registered in a future RFC, or a vendor-specific value. Vendor specific values MUST be prefixed with a domain name controlled by the vendor, e.g. "example.com/topsecret". Any value the client or server doesn't understand should be preserved but treated as equivalent to "private". o "public": The full details of the object are visible to those whom the object's calendar is shared with. o "private": The details of the object are hidden; only the basic time and metadata is shared. The following properties MAY be shared, any other properties MUST NOT be shared: * @type * created Jenkins & Stepanek Expires January 24, 2020 [Page 29] Internet-Draft JSCalendar July 2019 * due * duration * estimatedDuration * freeBusyStatus * privacy * recurrenceOverrides. Only patches which apply to another permissible property are allowed to be shared. * sequence * showWithoutTime * start * timeZone * timeZones * uid * updated o "secret": The object is hidden completely (as though it did not exist) when the calendar this object is in is shared. 4.4.4. replyTo Type: "String[String]" (optional). Represents methods by which participants may submit their RSVP response to the organizer of the calendar object. The keys in the property value are the available methods and MUST only contain ASCII alphanumeric characters (A-Za-z0-9). The value is a URI to use that method. Future methods may be defined in future specifications; a calendar client MUST ignore any method it does not understand, but MUST preserve the method key and URI. This property MUST be omitted if no method is defined (rather than an empty object). If this property is set, the "participants" property of this calendar object MUST contain at least one participant. The following methods are defined: Jenkins & Stepanek Expires January 24, 2020 [Page 30] Internet-Draft JSCalendar July 2019 o "imip": The organizer accepts an iMIP [RFC6047] response at this email address. The value MUST be a "mailto:" URI. o "web": Opening this URI in a web browser will provide the user with a page where they can submit a reply to the organizer. o "other": The organizer is identified by this URI but the method how to submit the RSVP is undefined. 4.4.5. participants Type: "Id[Participant]" (optional). A map of participant ids to participants, describing their participation in the calendar object. If this property is set, then the "replyTo" property of this calendar object MUST define at least one reply method. A Participant object has the following properties: o name: "String" (optional) The display name of the participant (e.g. "Joe Bloggs"). o email: "String" (optional) The email address for the participant. o sendTo: "String[String]" (mandatory) Represents methods by which the participant may receive the invitation and updates to the calendar object. The keys in the property value are the available methods and MUST only contain ASCII alphanumeric characters (A-Za-z0-9). The value is a URI to use that method. Future methods may be defined in future specifications; a calendar client MUST ignore any method it does not understand, but MUST preserve the method key and URI. This property MUST be omitted if no method is defined (rather than an empty object). The following methods are defined: * "imip": The participant accepts an iMIP [RFC6047] request at this email address. The value MUST be a "mailto:" URI. It MAY be different from the value of the participant's "email" property. Jenkins & Stepanek Expires January 24, 2020 [Page 31] Internet-Draft JSCalendar July 2019 * "other": The participant is identified by this URI but the method how to submit the invitation or update is undefined. o kind: "String" (optional) What kind of entity this participant is, if known. This MUST be either one of the following values, registered in a future RFC, or a vendor-specific value. Any value the client or server doesn't understand should be treated the same as if this property is omitted. * "individual": a single person * "group": a collection of people invited as a whole * "resource": a non-human resource, e.g. a projector * "location": a physical location involved in the calendar object that needs to be scheduled, e.g. a conference room. o roles: "String[Boolean]" (mandatory) A set of roles that this participant fulfills. At least one role MUST be specified for the participant. The keys in the set MUST be either one of the following values, registered in a future RFC, or a vendor-specific value: * "owner": The participant is an owner of the object. This signifies they have permission to make changes to it that affect the other participants. Non-owner participants may only change properties that just affect themself (for example setting their own alerts). * "attendee": The participant is an attendee of the calendar object. * "chair": The participant is in charge of the calendar object when it occurs. The value for each key in the set MUST be true. Roles that are unknown to the implementation MUST be preserved. o locationId: "String" (optional) The location at which this participant is expected to be attending. Jenkins & Stepanek Expires January 24, 2020 [Page 32] Internet-Draft JSCalendar July 2019 If the value does not correspond to any location id in the "locations" property of the JSCalendar object, this MUST be treated the same as if the participant's locationId were omitted. o participationStatus: "String" (optional, default: "needs-action") The participation status, if any, of this participant. The value MUST be either one of the following values, registered in a future RFC, or a vendor-specific value: * "needs-action": No status yet set by the participant. * "accepted": The invited participant will participate. * "declined": The invited participant will not participate. * "tentative": The invited participant may participate. o participationComment: "String" (optional) A note from the participant to explain their participation status. o attendance: "String" (optional, default: "required") The required attendance of this participant. The value MUST be either one of the following values, registered in a future RFC, or a vendor-specific value. Any value the client or server doesn't understand should be treated the same as "required". * "none": Indicates a participant who is copied for information purposes only. * "optional": Indicates a participant whose attendance is optional. * "required": Indicates a participant whose attendance is required. o expectReply: "Boolean" (optional, default: false) If true, the organizer is expecting the participant to notify them of their participation status. o scheduleSequence: "UnsignedInt" (optional, default: 0) Jenkins & Stepanek Expires January 24, 2020 [Page 33] Internet-Draft JSCalendar July 2019 The sequence number of the last response from the participant. If defined, this MUST be a non-negative integer. This can be used to determine whether the participant has sent a new RSVP following significant changes to the calendar object, and to determine if future responses are responding to a current or older view of the data. o scheduleUpdated: "UTCDateTime" (optional) The "updated" property of the last iTIP response from the participant. This can be compared to the "updated" property timestamp in future iTIP responses to determine if the response is older or newer than the current data. o invitedBy: "String" (optional) The participant id of the participant who invited this one, if known. o delegatedTo: "String[Boolean]" (optional) A set of participant ids that this participant has delegated their participation to. Each key in the set MUST be the id of a participant. The value for each key in the set MUST be true. This MUST be omitted if none (rather than an empty set). o delegatedFrom: "String[Boolean]" (optional) A set of participant ids that this participant is acting as a delegate for. Each key in the set MUST be the id of a participant. The value for each key in the set MUST be true. This MUST be omitted if none (rather than an empty set). o memberOf: "String[Boolean]" (optional) A set of group participants that were invited to this calendar object, which caused this participant to be invited due to their membership of the group(s). Each key in the set MUST be the id of a participant. The value for each key in the set MUST be true. This MUST be omitted if none (rather than an empty set). o linkIds: "String[Boolean]" (optional) A set of links to more information about this participant, for example in vCard format. The keys in the set MUST be the id of a Jenkins & Stepanek Expires January 24, 2020 [Page 34] Internet-Draft JSCalendar July 2019 Link object in the calendar object's "links" property. The value for each key in the set MUST be true. This MUST be omitted if none (rather than an empty set). 4.5. Alerts Properties 4.5.1. useDefaultAlerts Type: "Boolean" (optional, default: false). If true, use the user's default alerts and ignore the value of the "alerts" property. Fetching user defaults is dependent on the API from which this JSCalendar object is being fetched, and is not defined in this specification. If an implementation cannot determine the user's default alerts, or none are set, it MUST process the alerts property as if "useDefaultAlerts" is set to false. 4.5.2. alerts Type: "Id[Alert]" (optional). A map of alert ids to Alert objects, representing alerts/reminders to display or send to the user for this calendar object. An Alert Object has the following properties: o trigger: "OffsetTrigger|AbsoluteTrigger|UnknownTrigger" Defines when to trigger the alert. New types may be defined in future RFCs. An *OffsetTrigger* object has the following properties: * type: "String" (mandatory) The value of this property MUST be "offset". * offset: "SignedDuration" (mandatory). Defines the offset at which to trigger the alert relative to the time property defined in the "relativeTo" property of the alert. If the calendar object does not define a time zone, the user's default time zone SHOULD be used when determining the offset, if known. Otherwise, the time zone to use is implementation specific. * relativeTo: "String" (optional, default: "start") Jenkins & Stepanek Expires January 24, 2020 [Page 35] Internet-Draft JSCalendar July 2019 Specifies the time property that the alert offset is relative to. The value MUST be one of: + "start": triggers the alert relative to the start of the calendar object + "end": triggers the alert relative to the end/due time of the calendar object An *AbsoluteTrigger* object has the following properties: * type: "String" (mandatory) The value of this property MUST be "absolute". * when: "UTCDateTime" (mandatory). Defines a specific UTC date-time when the alert is triggered. An *UnknownTrigger* object is an object that contains a *type* property whose value is not recognized (i.e., not "offset" or "absolute"), plus zero or more other properties. This is for compatibility with client extensions and future RFCs. Implementations SHOULD NOT trigger for trigger types they do not understand, but MUST preserve them. o acknowledged: "UTCDateTime" (optional) This records when an alert was last acknowledged. This is set when the user has dismissed the alert; other clients that sync this property SHOULD automatically dismiss or suppress duplicate alerts (alerts with the same alert id that triggered on or before this date-time). For a recurring calendar object, the "acknowledged" property of the parent object MUST be updated, unless the alert is already overridden in the "recurrenceOverrides" property. Certain kinds of alert action may not provide feedback as to when the user sees them, for example email based alerts. For those kinds of alerts, this property SHOULD be set immediately when the alert is triggered and the action successfully carried out. o action: "String" (optional, default: "display") Describes how to alert the user. Jenkins & Stepanek Expires January 24, 2020 [Page 36] Internet-Draft JSCalendar July 2019 The value MUST be at most one of the following values, registered in a future RFC, or a vendor-specific value: * "display": The alert should be displayed as appropriate for the current device and user context. * "email": The alert should trigger an email sent out to the user, notifying about the alert. This action is typically only appropriate for server implementations. 4.6. Multilingual Properties 4.6.1. localizations Type: "String[PatchObject]" (optional). A map of [RFC5646] language tags to patch objects, which localize the calendar object into the locale of the respective language tag. See the description of PatchObject (Section 1.4.8) for the structure of the PatchObject. The patches are applied to the top-level calendar object. In addition, the "locale" property of the patched object is set to the language tag. All pointers for patches MUST end with one of the following suffixes; any patch that does not follow this MUST be ignored unless otherwise specified in a future RFC: o title o description o name For example, a patch to "recurrenceOverrides/2018-01- 05T14:00:00/locations/abcd1234/title" is permissible, but a patch to "uid" is not. Note that this specification does not define how to maintain validity of localized content. For example, a client application changing a JSCalendar object's title property might also need to update any localizations of this property. Client implementations SHOULD provide the means to manage localizations, but how to achieve this is specific to the application's workflow and requirements. 4.7. Time Zone Properties Jenkins & Stepanek Expires January 24, 2020 [Page 37] Internet-Draft JSCalendar July 2019 4.7.1. timeZone Type: "String|null" (optional, default: null). Identifies the time zone the object is scheduled in, or null for floating time. This is either a name from the IANA Time Zone Database [4] or the id of a custom time zone from the "timeZones" property (see Section 1.4.9). If omitted, this MUST be presumed to be null (i.e., floating time). 4.7.2. timeZones Type: "String[TimeZone]" (optional). Maps identifiers of custom time zones to their time zone definition. The following restrictions apply for each key in the map: o It MUST start with the "/" character (ASCII decimal 47; also see Sections 3.2.19 of [RFC5545] and 3.6. of [RFC7808] for discussion of the forward slash character in time zone identifiers). o It MUST be a valid "paramtext" value as specified in Section 3.1. of [RFC5545]. o At least one other property in the same JSCalendar object MUST reference a time zone using this identifier (i.e. orphaned time zones are not allowed). An identifier need only be unique to this JSCalendar object. A TimeZone object maps a VTIMEZONE component from iCalendar [RFC5545] and the semantics are as defined there. A valid time zone MUST define at least one transition rule in the "standard" or "daylight" property. Its properties are: o tzId: "String" (mandatory). The TZID property from iCalendar. o lastModified: "UTCDateTime" (optional) The LAST-MODIFIED property from iCalendar. o url: "String" (optional) The TZURL property from iCalendar. o validUntil: "UTCDateTime" (optional) Jenkins & Stepanek Expires January 24, 2020 [Page 38] Internet-Draft JSCalendar July 2019 The TZUNTIL property from iCalendar specified in [RFC7808]. o aliases: "String[Boolean]" (optional) Maps the TZID-ALIAS-OF properties from iCalendar specified in [RFC7808] to a JSON set of aliases. The set is represented as an object, with the keys being the aliases. The value for each key in the set MUST be true. o standard: "TimeZoneRule[]" (optional) The STANDARD sub-components from iCalendar. The order MUST be preserved during conversion. o daylight: "TimeZoneRule[]" (optional). The DAYLIGHT sub-components from iCalendar. The order MUST be preserved during conversion. A TimeZoneRule object maps a STANDARD or DAYLIGHT sub-component from iCalendar, with the restriction that at most one recurrence rule is allowed per rule. It has the following properties: o start: "LocalDateTime" (mandatory) The DTSTART property from iCalendar. o offsetTo: "String" (mandatory) The TZOFFSETTO property from iCalendar. o offsetFrom: "String" (mandatory) The TZOFFSETFROM property from iCalendar. o recurrenceRule: "RecurrenceRule" (optional) The RRULE property mapped as specified in Section 4.3.2. During recurrence rule evaluation, the "until" property value MUST be interpreted as a local time in the UTC time zone. o recurrenceDates: "LocalDateTime[Boolean]" (optional) Maps the RDATE properties from iCalendar to a JSON set. The set is represented as an object, with the keys being the recurrence dates. The value for each key in the set MUST be true. o names: "String[Boolean]" (optional) Jenkins & Stepanek Expires January 24, 2020 [Page 39] Internet-Draft JSCalendar July 2019 Maps the TZNAME properties from iCalendar to a JSON set. The set is represented as an object, with the keys being the names. The value for each key in the set MUST be true. o comments: "String[]" (optional). Maps the COMMENT properties from iCalendar. The order MUST be preserved during conversion. 5. Type-specific JSCalendar Properties 5.1. JSEvent Properties In addition to the common JSCalendar object properties (Section 4) a JSEvent has the following properties: 5.1.1. start Type: "LocalDateTime" (mandatory). The date/time the event starts in the event's time zone (as specified in the "timeZone" property, see Section 4.7.1). 5.1.2. duration Type: "Duration" (optional, default: "PT0S"). The zero or positive duration of the event in the event's start time zone. Note that a duration specified using weeks or days does not always correspond to an exact multiple of 24 hours. The number of hours/minutes/seconds may vary if it overlaps a period of discontinuity in the event's time zone, for example a change from standard time to daylight-savings time. Leap seconds MUST NOT be considered when computing an exact duration. When computing an exact duration, the greatest order time components MUST be added first, that is, the number of days MUST be added first, followed by the number of hours, number of minutes, and number of seconds. Fractional seconds MUST be added last. These semantics match the iCalendar DURATION value type ([RFC5545], Section 3.3.6). A JSEvent MAY involve start and end locations that are in different time zones (e.g. a trans-continental flight). This can be expressed using the "relativeTo" and "timeZone" properties of the JSEvent's Location objects (see Section 4.2.5). Jenkins & Stepanek Expires January 24, 2020 [Page 40] Internet-Draft JSCalendar July 2019 5.1.3. status Type: "String" (optional, default: "confirmed"). The scheduling status (Section 4.4) of a JSEvent. If set, it MUST be one of: o "confirmed": Indicates the event is definitely happening. o "cancelled": Indicates the event has been cancelled. o "tentative": Indicates the event may happen. 5.2. JSTask Properties In addition to the common JSCalendar object properties (Section 4) a JSTask has the following properties: 5.2.1. due Type: "LocalDateTime" (optional). The date/time the task is due in the task's time zone. 5.2.2. start Type: "LocalDateTime" (optional). The date/time the task should start in the task's time zone. 5.2.3. estimatedDuration Type: "Duration" (optional). Specifies the estimated positive duration of time the task takes to complete. 5.2.4. statusUpdatedAt Type: "UTCDateTime" (optional). Specifies the date/time the "status" property of either the task overall (Section 5.2.6) or a specific participant (Section 5.2.5) was last updated. If the task is recurring and has future instances, a client may want to keep track of the last status update timestamp of a specific task recurrence, but leave other instances unchanged. One way to achieve Jenkins & Stepanek Expires January 24, 2020 [Page 41] Internet-Draft JSCalendar July 2019 this is by overriding the statusUpdatedAt property in the task "recurrenceOverrides" property. However, this could produce a long list of timestamps for regularly recurring tasks. An alternative approach is to split the JSTask into a current, single instance of JSTask with this instance status update time and a future recurring instance. See also Section 4.1.3 on splitting. 5.2.5. progress In addition to the common properties of a Participant object (Section 4.4.5), a Participant within a JSTask supports the following property: o progress: ParticipantProgress (optional). The progress of the participant for this task, if known. This property MUST NOT be set if the "participationStatus" of this participant is any other value but "accepted". A ParticipantProgress object has the following properties: o status: "String" (mandatory) Describes the completion status of the participant's progress. The value MUST be at most one of the following values, registered in a future RFC, or a vendor-specific value: * "completed": The participant completed this task. * "in-process": The participant has started this task. * "failed": The participant failed to complete this task. o timestamp: "UTCDateTime" (mandatory) Represents the last time the participant progress was updated. 5.2.6. status Type: "String" (optional). Defines the overall status of this task. If omitted, the default status (Section 4.4) of a JSTask is defined as follows (in order of evaluation): o "completed": if the "status" property value of all participant progresses is "completed". Jenkins & Stepanek Expires January 24, 2020 [Page 42] Internet-Draft JSCalendar July 2019 o "failed": if at least one "status" property value of the participant progresses is "failed". o "in-process": if at least one "status" property value of the participant progresses is "in-process". o "needs-action": If none of the other criteria match. If set, it MUST be one of: o "needs-action": Indicates the task needs action. o "completed": Indicates the task is completed. o "in-process": Indicates the task is in process. o "cancelled": Indicates the task is cancelled. o "pending": Indicates the task has been created and accepted for processing, but not yet started. o "failed": Indicates the task failed. 5.3. JSGroup Properties JSGroup supports the following common JSCalendar properties (Section 4): o @type o uid o created o updated o categories o keywords o title o description o color o links Jenkins & Stepanek Expires January 24, 2020 [Page 43] Internet-Draft JSCalendar July 2019 In addition, the following JSGroup-specific properties are supported: 5.3.1. entries Type: "String[JSTask|JSEvent]" (mandatory). A collection of group members. This is represented as a map of the "uid" property value to the JSCalendar object member having that uid. Implementations MUST ignore entries of unknown type. 5.3.2. source Type: "String" (optional). The source from which updated versions of this group may be retrieved from. The value MUST be a URI. 6. Examples The following examples illustrate several aspects of the JSCalendar data model and format. The examples may omit mandatory or additional properties, which is indicated by a placeholder property with key "...". While most of the examples use calendar event objects, they are also illustrative for tasks. 6.1. Simple Event This example illustrates a simple one-time event. It specifies a one-time event that begins on January 15, 2018 at 1pm New York local time and ends at 2pm. { "@type": "jsevent", "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f1", "updated": "2018-01-01T12:00:00Z", "title": "Some event", "start": "2018-01-15T13:00:00", "timeZone": "America/New_York", "duration": "PT1H" } 6.2. Simple Task This example illustrates a simple task for a plain to-do item. Jenkins & Stepanek Expires January 24, 2020 [Page 44] Internet-Draft JSCalendar July 2019 { "@type": "jstask", "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2", "updated": "2018-01-19T18:00:00Z", "title": "Do something" } 6.3. Simple Group This example illustrates a simple calendar object group that contains an event and a task. { "@type": "jsgroup", "uid": "2a358cee-6489-4f14-a57f-c104db4dc343", "updated": "2018-01-15T18:00:00Z", "title": "A simple group", "entries": [ { "@type": "jsevent", "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f1", "updated": "2018-01-15T18:00:00Z", "title": "Some event", "start": "2018-01-15T13:00:00", "timeZone": "America/New_York", "duration": "PT1H" }, { "@type": "jstask", "uid": "2a358cee-6489-4f14-a57f-c104db4dc2f2", "updated": "2018-01-15T18:00:00Z", "title": "Do something" } ] } 6.4. All-day Event This example illustrates an event for an international holiday. It specifies an all-day event on April 1 that occurs every year since the year 1900. Jenkins & Stepanek Expires January 24, 2020 [Page 45] Internet-Draft JSCalendar July 2019 { "...": "", "title": "April Fool's Day", "showWithoutTime": true, "start": "1900-04-01T00:00:00", "duration": "P1D", "recurrenceRule": { "frequency": "yearly" } } 6.5. Task with a Due Date This example illustrates a task with a due date. It is a reminder to buy groceries before 6pm Vienna local time on January 19, 2018. The calendar user expects to need 1 hour for shopping. { "...": "", "title": "Buy groceries", "due": "2018-01-19T18:00:00", "timeZone": "Europe/Vienna", "estimatedDuration": "PT1H" } 6.6. Event with End Time Zone This example illustrates the use of end time-zones by use of an international flight. The flight starts on April 1, 2018 at 9am in Berlin local time. The duration of the flight is scheduled at 10 hours 30 minutes. The time at the flights destination is in the same time-zone as Tokyo. Calendar clients could use the end time-zone to display the arrival time in Tokyo local time and highlight the time- zone difference of the flight. The location names can serve as input for navigation systems. Jenkins & Stepanek Expires January 24, 2020 [Page 46] Internet-Draft JSCalendar July 2019 { "...": "", "title": "Flight XY51 to Tokyo", "start": "2018-04-01T09:00:00", "timeZone": "Europe/Berlin", "duration": "PT10H30M", "locations": { "2a358cee-6489-4f14-a57f-c104db4dc2f1": { "rel": "start", "name": "Frankfurt Airport (FRA)" }, "c2c7ac67-dc13-411e-a7d4-0780fb61fb08": { "rel": "end", "name": "Narita International Airport (NRT)", "timeZone": "Asia/Tokyo" } } } 6.7. Floating-time Event (with Recurrence) This example illustrates the use of floating-time. Since January 1, 2018, a calendar user blocks 30 minutes every day to practice Yoga at 7am local time, in whatever time-zone the user is located on that date. { "...": "", "title": "Yoga", "start": "2018-01-01T07:00:00", "duration": "PT30M", "recurrenceRule": { "frequency": "daily" } } 6.8. Event with Multiple Locations and Localization This example illustrates an event that happens at both a physical and a virtual location. Fans can see a live convert on premises or online. The event title and descriptions are localized. Jenkins & Stepanek Expires January 24, 2020 [Page 47] Internet-Draft JSCalendar July 2019 { "...": "", "title": "Live from Music Bowl: The Band", "description": "Go see the biggest music event ever!", "locale": "en", "start": "2018-07-04T17:00:00", "timeZone": "America/New_York", "duration": "PT3H", "locations": { "c0503d30-8c50-4372-87b5-7657e8e0fedd": { "name": "The Music Bowl", "description": "Music Bowl, Central Park, New York", "coordinates": "geo:40.7829,73.9654" } }, "virtualLocations": { "6f3696c6-1e07-47d0-9ce1-f50014b0041a": { "name": "Free live Stream from Music Bowl", "uri": "https://stream.example.com/the_band_2018" } }, "localizations": { "de": { "title": "Live von der Music Bowl: The Band!", "description": "Schau dir das groesste Musikereignis an!", "virtualLocations/6f3696c6-1e07-47d0-9ce1-f50014b0041a/name": "Gratis Live-Stream aus der Music Bowl" } } } 6.9. Recurring Event with Overrides This example illustrates the use of recurrence overrides. A math course at a University is held for the first time on January 8, 2018 at 9am London time and occurs every week until June 25, 2018 (inclusive). Each lecture lasts for one hour and thirty minutes and is located at the Mathematics department. This event has exceptional occurrences: at the last occurrence of the course is an exam, which lasts for 2 hours and starts at 10am. Also, the location of the exam differs from the usual location. On April 2 no course is held. On January 5 at 2pm is an optional introduction course, that occurs before the first regular lecture. Jenkins & Stepanek Expires January 24, 2020 [Page 48] Internet-Draft JSCalendar July 2019 { "...": "", "title": "Calculus I", "start": "2018-01-08T09:00:00", "timeZone": "Europe/London", "duration": "PT1H30M", "locations": { "2a358cee-6489-4f14-a57f-c104db4dc2f1": { "title": "Math lab room 1", "description": "Math Lab I, Department of Mathematics\n1 University Drive" } }, "recurrenceRule": { "frequency": "weekly", "until": "2018-06-25T09:00:00" }, "recurrenceOverrides": { "2018-01-05T14:00:00": { "title": "Introduction to Calculus I (optional)" }, "2018-04-02T09:00:00": { "excluded": true }, "2018-06-25T09:00:00": { "title": "Calculus I Exam", "start": "2018-06-25T10:00:00", "duration": "PT2H", "locations": { "2a358cee-6489-4f14-a57f-c104db4dc2f1": { "title": "Big Auditorium", "description": "Big Auditorium, Other Road" } } } } } 6.10. Recurring Event with Participants This example illustrates scheduled events. A team meeting occurs every week since January 8, 2018 at 9am Johannesburg time. The event owner also chairs the event. Participants meet in a virtual meeting room. An attendee has accepted the invitation, but on March 8, 2018 he is unavailable and declined participation for this occurrence, leaving a short explanation for the organizer. { "...": "", Jenkins & Stepanek Expires January 24, 2020 [Page 49] Internet-Draft JSCalendar July 2019 "title": "FooBar team meeting", "start": "2018-01-08T09:00:00", "timeZone": "Africa/Johannesburg", "duration": "PT1H", "virtualLocations": { "2a358cee-6489-4f14-a57f-c104db4dc2f1": { "name": "ChatMe meeting room", "uri": "https://chatme.example.com?id=1234567" } }, "recurrenceRule": { "frequency": "weekly" }, "replyTo": { "imip": "mailto:6489-4f14-a57f-c1@schedule.example.com" }, "participants": { "dG9tQGZvb2Jhci5leGFtcGxlLmNvbQ": { "name": "Tom Tool", "email": "tom@foobar.example.com", "sendTo": { "imip": "mailto:41f3-8b10-516a4d0f42bc@calendar.example.com" }, "participationStatus": "accepted", "roles": { "attendee": true } }, "em9lQGZvb2Jhci5leGFtcGxlLmNvbQ": { "name": "Zoe Zelda", "email": "zoe@foobar.example.com", "sendTo": { "imip": "mailto:zoe@foobar.example.com" }, "participationStatus": "accepted", "roles": { "owner": true, "attendee": true, "chair": true } }, "...": "" }, "recurrenceOverrides": { "2018-03-08T09:00:00": { "participants/dG9tQGZvb2Jhci5leGFtcGxlLmNvbQ/participationStatus": "declined", "participants/dG9tQGZvb2Jhci5leGFtcGxlLmNvbQ/participationComment": Jenkins & Stepanek Expires January 24, 2020 [Page 50] Internet-Draft JSCalendar July 2019 "Sorry, kid's recital this week, can't make it." } } } 7. Security Considerations Calendaring and scheduling information is very privacy-sensitive. The transmission of such information must be careful to protect it from possible threats, such as eavesdropping, replay, message insertion, deletion, modification, and man-in-the-middle attacks. This document just defines the data format; such considerations are primarily the concern of the API or method of storage and transmission of such files. 7.1. Expanding Recurrences A recurrence rule may produce infinite occurrences of an event. Implementations MUST handle expansions carefully to prevent accidental or deliberate resource exhaustion. Conversely, a recurrence rule may be specified that does not expand to anything. It is not always possible to tell this through static analysis of the rule, so implementations MUST be careful to avoid getting stuck in an infinite loop, or otherwise exhausting resources, searching for the next occurrence. 7.2. JSON Parsing The Security Considerations of [RFC8259] apply to the use of JSON as the data interchange format. As for any serialization format, parsers need to thoroughly check the syntax of the supplied data. JSON uses opening and closing tags for several types and structures, and it is possible that the end of the supplied data will be reached when scanning for a matching closing tag; this is an error condition, and implementations need to stop scanning at the end of the supplied data. JSON also uses a string encoding with some escape sequences to encode special characters within a string. Care is needed when processing these escape sequences to ensure that they are fully formed before the special processing is triggered, with special care taken when the escape sequences appear adjacent to other (non-escaped) special characters or adjacent to the end of data (as in the previous paragraph). Jenkins & Stepanek Expires January 24, 2020 [Page 51] Internet-Draft JSCalendar July 2019 If parsing JSON into a non-textual structured data format, implementations may need to allocate storage to hold JSON string elements. Since JSON does not use explicit string lengths, the risk of denial of service due to resource exhaustion is small, but implementations may still wish to place limits on the size of allocations they are willing to make in any given context, to avoid untrusted data causing excessive memory allocation. 7.3. URI Values Several JSCalendar properties contain URIs as values, and processing these properties requires extra care. Section 7 of [RFC3986] discusses security risk related to URIs. 8. IANA Considerations This document defines a MIME media type for use with JSCalendar data formatted in JSON. Type name: application Subtype name: jscalendar+json Required parameters: type The "type" parameter conveys the type of the JSCalendar data in the body part, with the value being one of "jsevent", "jstask", or "jsgroup". The parameter MUST NOT occur more than once. It MUST match the value of the "@type" property of the JSON-formatted JSCalendar object in the body. Optional parameters: none Encoding considerations: Same as encoding considerations of application/json as specified in RFC8529, Section 11 [RFC8259]. Security considerations: See Section 7 of this document. Interoperability considerations: This media type provides an alternative to iCalendar, jCal and proprietary JSON-based calendaring data formats. Published specification: This specification. Applications that use this media type: Applications that currently make use of the text/calendar and application/calendar+json media types can use this as an alternative. Similarly, applications Jenkins & Stepanek Expires January 24, 2020 [Page 52] Internet-Draft JSCalendar July 2019 that use the application/json media type to transfer calendaring data can use this to further specify the content. Fragment identifier considerations: N/A Additional information: Magic number(s): N/A File extensions(s): N/A Macintosh file type code(s): N/A Person & email address to contact for further information: calext@ietf.org Intended usage: COMMON Restrictions on usage: N/A Author: See the "Author's Address" section of this document. Change controller: IETF 9. Acknowledgments The authors would like to thank the members of CalConnect for their valuable contributions. This specification originated from the work of the API technical committee of CalConnect, the Calendaring and Scheduling Consortium. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2392] Levinson, E., "Content-ID and Message-ID Uniform Resource Locators", RFC 2392, DOI 10.17487/RFC2392, August 1998, . [RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet: Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002, . Jenkins & Stepanek Expires January 24, 2020 [Page 53] Internet-Draft JSCalendar July 2019 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, DOI 10.17487/RFC3986, January 2005, . [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally Unique IDentifier (UUID) URN Namespace", RFC 4122, DOI 10.17487/RFC4122, July 2005, . [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, . [RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault, "Calendaring Extensions to WebDAV (CalDAV)", RFC 4791, DOI 10.17487/RFC4791, March 2007, . [RFC5545] Desruisseaux, B., Ed., "Internet Calendaring and Scheduling Core Object Specification (iCalendar)", RFC 5545, DOI 10.17487/RFC5545, September 2009, . [RFC5546] Daboo, C., Ed., "iCalendar Transport-Independent Interoperability Protocol (iTIP)", RFC 5546, DOI 10.17487/RFC5546, December 2009, . [RFC5646] Phillips, A., Ed. and M. Davis, Ed., "Tags for Identifying Languages", BCP 47, RFC 5646, DOI 10.17487/RFC5646, September 2009, . [RFC5870] Mayrhofer, A. and C. Spanring, "A Uniform Resource Identifier for Geographic Locations ('geo' URI)", RFC 5870, DOI 10.17487/RFC5870, June 2010, . [RFC6047] Melnikov, A., Ed., "iCalendar Message-Based Interoperability Protocol (iMIP)", RFC 6047, DOI 10.17487/RFC6047, December 2010, . [RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type Specifications and Registration Procedures", BCP 13, RFC 6838, DOI 10.17487/RFC6838, January 2013, . Jenkins & Stepanek Expires January 24, 2020 [Page 54] Internet-Draft JSCalendar July 2019 [RFC6901] Bryan, P., Ed., Zyp, K., and M. Nottingham, Ed., "JavaScript Object Notation (JSON) Pointer", RFC 6901, DOI 10.17487/RFC6901, April 2013, . [RFC7265] Kewisch, P., Daboo, C., and M. Douglass, "jCal: The JSON Format for iCalendar", RFC 7265, DOI 10.17487/RFC7265, May 2014, . [RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493, DOI 10.17487/RFC7493, March 2015, . [RFC7529] Daboo, C. and G. Yakushev, "Non-Gregorian Recurrence Rules in the Internet Calendaring and Scheduling Core Object Specification (iCalendar)", RFC 7529, DOI 10.17487/RFC7529, May 2015, . [RFC7808] Douglass, M. and C. Daboo, "Time Zone Data Distribution Service", RFC 7808, DOI 10.17487/RFC7808, March 2016, . [RFC7986] Daboo, C., "New Properties for iCalendar", RFC 7986, DOI 10.17487/RFC7986, October 2016, . [RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, . [RFC8288] Nottingham, M., "Web Linking", RFC 8288, DOI 10.17487/RFC8288, October 2017, . 10.2. Informative References [MIME] "IANA Media Types", . 10.3. URIs [1] https://www.iana.org/time-zones [2] https://www.iana.org/assignments/link-relations/link- relations.xhtml Jenkins & Stepanek Expires January 24, 2020 [Page 55] Internet-Draft JSCalendar July 2019 [3] https://www.w3.org/TR/2011/REC-css3-color-20110607/#svg-color [4] https://www.iana.org/time-zones Authors' Addresses Neil Jenkins Fastmail PO Box 234 Collins St West Melbourne VIC 8007 Australia Email: neilj@fastmailteam.com URI: https://www.fastmail.com Robert Stepanek Fastmail PO Box 234 Collins St West Melbourne VIC 8007 Australia Email: rsto@fastmailteam.com URI: https://www.fastmail.com Jenkins & Stepanek Expires January 24, 2020 [Page 56]